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Cytogenetic study of Allocebus trichotis a Malagasy prosimian.

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American Journal of Primatology 36239-244 (1995)
Cytogenetic Study of Allocebus trichotis, a
Malagasy Prosimian
Y. RUMPLER', S. WARTER', M. HAUWY', B. MEIER4, A. PEYRIERAS5,
R. ALBIGNAC3, J.J. PETTER3 AND B. DUTRILLAUX'
'Facult6 de Medecine, Institut d'Embryologie de Strasbourg, 'Institut Curie, URA No. 118,
CNRS, and 3Parc Zoologique de Vincennes, Museum National &Histoire Naturelle, Paris,
France; 4Medizinische Fakultat, Institut fur Anatomie, Bochum, Germany; 'B.P. 6218,
Tananariue, Madagascar
A cytogenetic study of a female Allocebus trichotis was conducted using R-,
G-, and C-banding. Its karyotype does not differ from those of the other
Cheirogaleinae (Microcebus, Cheirogaleus, and Mirza). The absence of
chromosomal rearrangement in speciation in this group is discussed.
0 1995 Wiley-Liss, Inc.
Key words: lemur, AZZocebus trichotis, cytogenetics
INTRODUCTION
According to the classification of Tattersall [19821 and Rumpler [19901, the
family Cheirogaleidae, prosimians of Madagascar, comprises five genera: Phaner,
Microcebus, Cheirogaleus, Mirza, and Allocebus. Cytogenetic studies of the first
four reveals that Microcebus, Cheirogaleus, and Mirza are characterized by the
same karyotype (2N = 66) but that Cheirogaleus has a large amount of heterochromatin [Rumpler & Dutrillaux, 19791. Phaner, on the other hand, displays a
different karyotype (2N = 46) [Rumpler & Dutrillaux, 19791, and it was suggested
that this species be classified in a separate subfamily: the Phanerinae [Rumpler &
Rakotosamimanana, 19711. The Cheirogaleidae will thus comprise two subfamilies: Cheirogaleinae and Phanerinae.
The only member of this family whose karyotype remains unknown is Allocebus. Allocebus was first described by Gunther (1875) as Cheirogaleus trichotis,
and only a few specimens were found [Hill, 19531until Peyrieras discovered a new
specimen named Allocebus trichotis by Petter-Rousseaux and Petter [19671. No
further specimens were captured until 1990, when B. Meier captured several specimens, of which two are still housed at the Parc Zoologique de Vincennes, Paris.
This paper presents the karyotype of these animals.
MATERIALS AND METHODS
The subjects were one female and one male Allocebus trichotis kept in captivity. Cytogenetic investigation was conducted on both lymphocyte cultures and
Received for publication November 15, 1993; revision accepted November 21, 1994.
Address reprint requests to Yves Rumpler, Universite Louis Pasteur, Faculte de Medecine, Institut
d'Embryologie, 11 rue Humann, 67085-Strasbourg cedex, France.
0 1995 Wiley-Liss, Inc.
240 / Rumpler et al.
Allocebus
trichotis
Fig. 1. R-banded karyotype of a female Allocebus trichotis.
Cytogenetics of Allocebus trichotis I 241
Fig. 2. G-banded karyotype of a male Allocebus trichotis.
242 / Rumpler et al.
Fig. 3. Partial C-banded metaphase. Some microchromosomes are completely stained
with C-bands (open arrowheads). On some chromosomes, heterochromatin blocks are also
located elsewhere than on the juxtacentromeric region (solid arrowheads).
fibroblast cultures, derived from a skin biopsy done under general anaesthesia
(ketamine chlorhydrate 0.100 mg). The karyotype was established after Q-banding
CCasperson et al., 19701, R-banding [Dutrillaux & Lejeune, 19711, G-banding [Seabright, 19711, and C-banding [Sumner, 19721.
RESULTS AND DISCUSSION
The diploid number was determined on 54 metaphases. The karyotype (Figs. 1,
2) comprises 66 chromosomes, all acrocentric, except the X, which is metacentric.
C-bands (Fig. 3) and Q-bands reveal no heterochromatic peculiarities save for some
microchromosomes completely stained with C-bands or heterochromatic blocks
located outside the juxtacentromeric region on some autosomes (Fig. 3). R-banding
as well as Q- and G-banding allowed us to pair all the large and medium chromosomes with a high degree of certainty. Determination of the pairing of the small
chromosomes remains uncertain (Figs. 1, 2, 4).
The comparative study of the karyotype of A. trichotis reveals no apparent
differences from those of Microcebus murinus, Cheirogaleus, and Mirza (Fig. 4).
The existence of such similar karyotypes for these four genera, except for the
amount and the localization of heterochromatin, calls attention to the following:
1. The chromosomal evolution of the Cheirogaleinae differs from that of all other
lemurs. In the other families, each species examined thus far is characterized by a
specific karyotype resulting from chromosomal rearrangements which occurred in
a predominant mode, called orthoselection by White [1978], and which is different
for each family: Robertsonian translocations represent the major mode in the Lemuridae, termino-terminal fusions are the most frequent in the Lepilemuridae,
Cytogenetics of Allocebus trichotis I 243
Microcebus-Allocebus
Fig. 4. Half R-banded karyotype of Microcebus (left)and AZZocebus (right).
244 / Rumpler et al.
and pericentric inversions are frequent only in the Indriidae. Thus, only a small
number of rearrangements characterize the subfamily Cheirogaleinae; none occurred in the hypothetical ancestral karyotype of all lemurs common to this group
which thus remains very ancestral. Nevertheless, the genus Phaner, which also
belongs to the same family, the Cheirogaleidae, showed the same mode of chromosomal evolution as the other lemur families.
2. Although chromosomal rearrangements played a n important role during
evolution of most species, the Cheirogaleinae illustrate a form of speciation that
does not involve chromosomal rearrangement.
3. The last point is that, in this particular case, cytogenetics is unable to
contribute towards establishing a phylogeny of the Cheirogaleinae, and, hence, the
systematic position of Allocebus remains as controversial as ever in this subfamily,
even if i t appears closer to Microcebus, Cheirogaleus, and Mirza than Phaner.
CONCLUSIONS
1. The cytogenetic study of Allocebus trichotis reveals that its karyotype is
similar to that of the other Cheirogaleinae, Microcebus, Cheirogaleus, and Mirza.
This reinforces the peculiarity of this group, characterized by a speciation not
involving chromosomal rearrangement.
ACKNOWLEDGMENTS
We are grateful to Mr. G. Cadiou for his photograph work, Mrs M. Lavaux for
her secretarial assistance, and Professor G.A. Doyle for correcting the English
version of this manuscript.
REFERENCES
Casperson, T.; Zech, L.; Johansson, C. Analysis of human metaphase chromosome set
by aid of DNA-binding fluorescent agents.
EXPERIMENTAL CELL RESEARCH 62:
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Dutrillaux, B.; Lejeune, J. Sur une nouvelle
technique d'analyse du caryotype humain.
COMPTES RENDUS DE L'ACADEMIE
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Hill, W.C.O. COMPARATIVE ANATOMY
AND TAXONOMY OF THE PRIMATES.
I. STREPSIRHINI. Edinburgh, University
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Petter-Rousseaux, A.; Petter, J.J. Contribution a la systematique des Cheirogaleidae
(Lemuriens malgaches): Allocebus genre
nouveau, pour Cheirogaleus trichotis,
Gunther, 1875. MAMMALIA 31574-582,
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Rumpler, Y. Systematique des lemuriens.
PD.13-22 in PRIMATES. RECHERCHES
A'CTUELLES. J.J. Roeder; J. Anderson.
Masson, ed. Paris, 1990.
Rumpler, Y.; Dutrillaux, B. Chromosomal
evolution in Malagasy lemurs. IV. Chromosomal studies in the genus Phaner,
Varecia, Lemur, Microcebus and Cheirogaleus. CYTOGENETIC AND CELL GENETICS 24:224-232, 1979.
Rumpler, Y.; Rakotosamimana, B. Coussinets plantaires et dermatoglyphes de representants de lemuriformes malgaches.
BULLETIN DE L'ASSOCIATION DES
ANATOMISTES 54:493-510,1971,
Seabright, M. A rapid banding technique for
human chromosomes. LANCET 971:1971.
Sumner, A.T. A simple technique for demonstrating centromeric heterochromatin. EXPERIMENTAL CELL RESEARCH 75:
304-305,1972,
Tattersall, I. THE PRIMATES OF MADAGASCAR. New York, Columbia University
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White, M.J.D. MODES OF SPECIATION.
San Francisco. W. Freeman and Co.. eds.
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